According to Rand Paul (Ky.) — one of four GOP senators on record supporting the Democrats’ resolution to overturn President Trump’s national emergency declaration — as many as 10 Republicans could buck the White House and vote with Democrats next week.

The president is reportedly upping the pressure on Republicans. On Wednesday afternoon, he tweeted: “Senate Republicans are not voting on constitutionality or precedent, they are voting on desperately needed Border Security & the Wall. Our Country is being invaded with Drugs, Human Traffickers, & Criminals of all shapes and sizes. That’s what this vote is all about. STAY UNITED!”

Two of the four senators who will be voting to annul Trump’s executive order are up for reelection in 2020: Susan Collins of Maine and Thom Tillis of North Carolina. The others are Paul and Lisa Murkowski of Alaska. With their support and that of all Democrats, the resolution would pass the Senate and force Trump to issue the first veto of his presidency.

Many GOP senators who support the wall were against Trump usurping the power of Congress to build his border wall through emergency declaration. But, here are at least seven definitive holdouts listed from least to most likely to vote against the president based on previous statements and what they have to gain or lose.

7. Ted Cruz (Texas)

Cruz has made his concerns clear that Trump issuing a national emergency could be a “slippery slope” for future Democratic presidents to use such powers to declare their policy priorities an emergency. It would make sense that Cruz, an expert in constitutional law, would be uncomfortable with this move, and if it had been done by a Democratic president he would certainly be among those protesting the loudest about executive overreach. But after a bitter start to their relationship when he and Trump were opponents in the 2016 primary, Cruz has come around to being an ally on Capitol Hill and owes Trump for holding a huge rally for him last year when Cruz was in a very tight race to retain his Senate seat.

6. Patrick J. Toomey (Pennsylvania)

Toomey is not one to shy away from taking a contentious stance (see: background checks on firearms), but most of the time he falls in line with the party. But Toomey represents a state that swings with the political winds, and if he were up for reelection sooner, he might be closer to the top of this list. But Toomey has his seat secured for another four years and may see more benefit in staying in Trump’s good graces.

5. Mitt Romney (Utah)

When Romney arrived in Washington, but before he was sworn in, he penned an op-ed in The Washington Post about how he will stand up to Trump when warranted, but in his first two months, Romney has not done so. This could be Romney’s big moment to take a stand against the president, but, despite his critiques of the move, he has been fairly neutral in his condemnations of it.

4. Mike Lee (Utah)

Lee hails from the same camp as Paul when it comes to federal government overreach, and he is no fan of Congress ceding power to the executive branch. Lee could really go either way, but if he sticks with his convictions, he will vote against the president. Lee also likens himself a constitutional purist.

3. Marco Rubio (Florida)

Rubio is usually a team player, but he has said he is unlikely to support Trump on this one. He sees it as a clear violation of the Constitution. “I will wait to see what statutory or constitutional power the president relies on to justify such a declaration before making any definitive statement. But I am skeptical it will be something I can support,” Rubio said in a statement last month. Certainly the White House is working hard to change his mind, and it is not out of the question that Rubio would find a way to justify standing with the president. Like Toomey, Rubio has his seat for another four years, so this issue is unlikely to dog him by the time he is up for reelection.

2. Cory Gardner (Colo.)

Of all the possible Republican defectors, Gardner has the most to lose. He is up for reelection in 2020 in a purple state that Hillary Clinton won in 2016 by 5 points. Taking the president’s side on this could jeopardize his already tenuous reelection prospects, but voting against the president will invite the wrath of Trump’s core supporters who make up a large share of the loyal GOP voting constituencies.

1. Lamar Alexander (Tenn.)

Alexander has the least to lose. He is retiring after this term, so he is unshackled to anyone. Considered a moderate for these times, he has tried to persuade the White House to reverse course and find the funds from other pools of money that do not require the president to declare an emergency.